const QUOTE: char = '"';

/// Slice a string between quotes
pub trait Unquote<'a> {
    /// Whether the input is quoted. If this is false the fallible methods of
    /// this interface will fail.
    fn is_quoted(&self) -> bool;

    /// Unquotes a string. If the input is not quoted it is simply returned
    /// as-is. If the input is partially quoted on either end that quote is not
    /// removed.
    fn unquote(&self) -> Option<&'a str>;

    /// Unquotes a string. The input must be quoted on each side for Some to be
    /// returned
    fn unquote_infallible(&self) -> &'a str;
}

impl<'a> Unquote<'a> for &'a str {
    #[inline]
    fn unquote_infallible(&self) -> &'a str {
        self.strip_prefix(QUOTE)
            .unwrap_or(self)
            .strip_suffix(QUOTE)
            .unwrap_or(self)
    }

    #[inline]
    fn unquote(&self) -> Option<&'a str> {
        self.strip_prefix(QUOTE).and_then(|s| s.strip_suffix(QUOTE))
    }

    #[inline]
    fn is_quoted(&self) -> bool {
        self.starts_with(QUOTE) && self.ends_with(QUOTE)
    }
}
